Physicochemical characteristics and in vitro digestibility ofindica,japonica, and waxy type rice flours and their derived resistant starch type III products

Abstract

Physicochemical and in vitro digestibility of three types of rice flours with different amylose contents, namely, indica (IR), japonica (JR) and japonica waxy (WR), and their derived resistant starch (RS) products prepared with treatments involving pullulanase debranching followed by a one cycle of freeze–thaw process were assessed. The native rice flours displayed a typical A-type polymorph with different crystallinity levels closely related to the amylopectin content and the enthalpy change. The nonwaxy rice flours, especially IR, showed a more restricted-swelling pasting behavior, a higher gelatinization temperature, and a lower glycemic response than WR. Significant differences in glycemic response between the rice flours were associated with amylose and RS contents and breakdown viscosity. The RS products had a substantial increase in amylose and RS contents. The process for obtaining RS changed the crystallinity pattern to a mixture of B- and V-type polymorphs and increased the crystallinity. The RS products showed less pronounced changes in pasting behavior and enhanced thermostability. The rate and extent of starch digestion were significantly decreased in the RS products, and the highest RS and the lowest estimated glycemic index was seen for the RS product produced from WR.